1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in association with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
One of factors which determine the performances of the recording head is throat height (TH). The throat height is a length (height) of a magnetic pole from the air bearing surface to the edge of an insulating layer for electrically isolating a thin film coil for generating a magnetic flux. The air bearing surface is a surface of a thin film magnetic head, which faces a magnetic recording medium and is also called a track surface. In order to improve the performances of the recording head, reduction in throat height is desired. The throat height is controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the recording density in the performances of the recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring now to FIGS. 30 to 35, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in FIG. 30, an insulating layer 102 made of, for example, alumina (Al2O3) is deposited in thickness of about 5 to 10 xcexcm on a substrate 101 made of altic (Al2O3 with TiC) or the like. Subsequently, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. For example, alumina is then deposited by sputtering in thickness of 100 to 200 nm on the bottom shield layer 103 to form a shield gap film 104. An MR film 105 for constructing an MR device for reproduction is deposited on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers which are electrically connected to the MR film 105 are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104, and the MR film 105, and the MR film 105 is buried in the shield gap films 104 and 106. An upper shield-cum-bottom pole (hereinbelow, referred to as a bottom pole) 107 made of a magnetic material such as Permalloy (NiFe) used for both of the reproducing head and the recording head is formed on the shield gap film 106.
As shown in FIG. 31, on the bottom pole 107, a write gap layer 108 made of an insulating material such as alumina is formed. On the write gap layer 108, a thin film coil 109 for an inductive recording head made of, for example, copper (Cu) is formed by plating or the like. Subsequently, a photoresist layer 110 is formed in a predetermined pattern by high-precision photolithography so as to cover the thin film coil 109. In order to flatten the thin film coil 109 and insulate turns of the thin film coil 109 from each other, a heat treatment is performed at, for example, 250xc2x0
As shown in FIG. 32, in a position rearward of the thin film coil 109 (right side in FIG. 32), an opening 108a is formed by partially etching the write gap layer 108 in order to form a magnetic path. Then, a top yoke-cum-top magnetic pole (hereinbelow, called a top pole) 111 made of a magnetic material such as Permalloy for the recording head is selectively formed on the write gap layer 108 and the photoresist layer 110. The top pole 111 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108a. The top pole 111 is used as a mask and the write gap layer 108 and the bottom pole 107 are etched by about 0.5 xcexcm through ion milliing. After that, an overcoat layer 112 made of, for example, alumina is formed on the top pole 111. Finally, a slider is machined to thereby form a track surface (air bearing surface) 120 of the recording head and the reproducing head. In such a manner, a thin film magnetic head is completed.
FIGS. 33 to 35 show the structure of the thin film magnetic head in a completed state. FIG. 33 is a cross section of the thin film magnetic head perpendicular to the air bearing surface 120. FIG. 34 is an enlarged cross section parallel to the air bearing surface 120 of the pole part. FIG. 35 is a plan view. Each of FIGS. 30 to 33 is a cross section taken along line A-Axe2x80x2 of FIG. 35. In FIGS. 33 to 35, the overcoat layer 112 is not shown.
In order to improve the performance of the thin film magnetic head, it is important to form the head with accurate throat height TH, apex angle xcex8, pole width P2W and pole length P2L shown in FIGS. 33 and 34. The apex angle xcex8 is an angle formed by a straight line which is in contact with a side face on the track face side of the photoresist layer 110 and the top face of the top pole 111. The pole width P2W defines the width of a recording track on a recording medium. The pole length P2L indicates the thickness of the pole. In FIGS. 33 and 35, xe2x80x9cTH0 positionxe2x80x9d denotes the edge on the track face side of the photoresist layer 110 as an insulating layer which electrically isolates the turns of the thin film coil 109, that is, a reference position 0 of the throat height TH.
As shown in FIG. 34, a structure in which side walls of the top pole 111, the write gap layer 108 and a part of the bottom pole 107 are formed vertically in a self-aligned manner is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. As shown in FIG. 34, lead layers 121 as a lead electrode layer electrically connected to the MR film 105 are provided on both sides of the MR film 105. In FIGS. 30 to 33, the lead layers 121 are omitted.
FIG. 36 shows the structure in plan view of the top pole 111. As shown in the diagram, the top pole 111 has a yoke 111a which occupies a major part of the top pole 111 and a pole tip 111b having an almost constant width W100 as the pole width P2W. In the coupling portion between the yoke 111a and the pole tip 111b, the outer periphery of the yoke 111a forms an angle a to a plane parallel to the air bearing surface 120. In the coupling portion, the outer periphery of the pole tip 111b forms an angle xcex2 to a plane parallel to the air bearing surface 120. For example, a is about 45 degrees and xcex2 is 90 degrees. The width of the pole tip 111b defines the width of a recording track on a recording medium. The pole tip 111b includes a portion F on the front side (the air bearing surface 120 side) with respect to the position TH0 and a portion R on the rear side (on the yoke 111a side) with respect to the position TH0. As understood from FIG. 33, the portion F extends on the flat write gap layer 108, and the portion R and the yoke 111a extend on a coil portion (hereinbelow, called an xe2x80x9capex portionxe2x80x9d which is covered with the photoresist layer 110 and is raised like a mountain).
The shape of the top pole is described in, for example, Japanese Unexamined Patent Publication No. Hei 8-249614.
Since the pole width P2W determines the track width of the recording head, accurate formation is required. Especially, in recent years, in order to realize high surface density recording, that is, to form a recording head of a narrow track structure, a microfabrication of setting the pole width P2W of the top pole to 1.0 xcexcm or less is demanded.
As a method of forming the top pole, for example, as disclosed in Japanese Unexamined Patent Publication No. Hei 7-262519, a frame plating method is used. In the case of forming the top pole 111 by using the frame plating method, first, a thin electrode film made of, for example, Permalloy is deposited on the whole apex portion by sputtering or the like. A photoresist is then applied on the electrode film and is patterned by a photolithography process to form a frame (outer frame) for plating. By using the electrode film formed before as a seed layer, the top pole 111 is formed by plating.
There is a level difference of, for example, larger than 3 to 4 xcexcm between the apex portion and the other portion. A photoresist is applied on the apex portion in thickness of 3 to 4 xcexcm. When it is assumed that at least 3 xcexcm of thickness of the photoresist on the apex portion is necessary, since the photoresist having fluidity gathers in the lower part, a photoresist film in thickness of, for example, larger than 4 to 6 xcexcm is formed below the apex portion.
In order to form a narrow track as described above, it is necessary to form a frame pattern having a width of about 1.0 xcexcm by a photoresist film. That is, a fine pattern having a width of 1.0 xcexcm or less has to be formed by a photoresist film having a thickness of 4 to 6 xcexcm or more. It is, however, extremely difficult to form such a thick photoresist pattern in width of the narrower pattern in a manufacturing process.
Moreover, at the exposure time of photolithography, light for exposure is reflected by an electrode underlayer as a seed layer. The photoresist also senses the reflection light, so that a deformation or the like occurs in the photoresist pattern and a sharp and accurate photoresist pattern cannot be obtained. As a result, the top pole cannot be formed in a desired shape. For example, the shape of the side walls of the top pole is rounded. Particularly, when the pole width P2W is further reduced to W100A as shown in FIG. 37, it becomes more difficult to obtain the desired width W100A for the following reason. In the portion R extending over the apex portion of the pole tip 111b, the light reflected by the electrode underlayer includes not only reflection light in the vertical direction but also reflection light in the oblique or lateral direction from the inclined face of the apex portion. The reflection light exerts an influence on photosensitivity of the photoresist layer. As a result, the width of the photoresist pattern which defines the pole width P2W becomes wider than an expected value and the shape becomes as shown by solid lines in FIG. 37. In the pole tip 111b, the width of the front portion F with respect to the TH0 position is an extremely important factor of defining the track width on a recording medium. When the width of the portion F becomes wider than the above value W100A, a target fine track width cannot be obtained.
The above-mentioned magnetic head disclosed in Japanese Unexamined Patent Publication No. Hei 8-249614 also has a similar problem. In the magnetic head disclosed in the publication, the width of the magnetic pole changes gently from the TH0 position toward the yoke. Consequently, due to an influence of reflection light in the oblique or lateral direction from the inclined face of the apex portion exerted on the photosensitivity of the photoresist layer, the width of the front portion with respect to the TH0 position cannot be accurately controlled.
As shown in FIG. 37, since the portion R extending from the TH0 position to the coupling portion with the yoke 111a in the pole tip 111b has almost the same width as that of the front portion F with respect to the TH0 position and the cross sectional area of the portion R is small, the magnetic flux from the yoke 111a is saturated in the portion R and cannot sufficiently reach the portion F which defines the track width. As a result, the overwrite characteristic, that is, a characteristic in the case of overwriting data on a recording medium on which data has been already written becomes as low as, for example, about 10 to 20 dB. There is a problem such that a sufficient overwrite characteristic cannot be assured.
The invention has been achieved in consideration of the problems and its object is to provide a thin film magnetic head, in which the pole width can be accurately controlled and a sufficient overwrite characteristic can be obtained even when the pole width is reduced, and a method of manufacturing the head.
According to the invention, there is provided a thin film magnetic head including: two magnetic layers magnetically coupled to each other and having respectively two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein one of the two magnetic layers includes: a first magnetic portion which extends so as to be apart from the recording-medium-facing surface; and a second magnetic portion which partially overlaps with the first magnetic portion and is magnetically coupled to the first magnetic portion in an overlap region where the first and second magnetic portions overlap with each other, the other magnetic layer in the two magnetic layers extends so as to be apart from the recording-medium-facing surface, and a magnetic shield layer for suppressing propagation of a magnetic flux between the first magnetic and the other magnetic portion is formed in at least the overlap region so as to be adjacent to the gap layer.
According to the invention, there is provided a method of manufacturing a thin film magnetic head including: two magnetic layers magnetically coupled to each other and having respectively two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the method comprising the steps of: forming one of the two magnetic layers so as to include: a first magnetic portion which extends so as to be apart from the recording-medium-facing surface; and a second magnetic portion which partially overlaps with the first magnetic portion and is magnetically coupled to the first magnetic portion in an overlap region where the first and second magnetic portions overlap with each other; forming the other magnetic layer of the two magnetic layers which extends so as to be apart from the recording-medium-facing surface; and forming a magnetic shield layer for suppressing propagation of a magnetic flux between the first magnetic portion and the other magnetic layer at least in an overlap region so as to be adjacent to the gap layer.
In the thin film magnetic head of the invention, the second magnetic portion in one of the magnetic layers overlaps with a part of the first magnetic portion, and thereby the first and second magnetic portions are magnetically coupled. By the magnetic shield layer formed in the overlap region in which the first and second magnetic portions overlap with each other so as to be adjacent to the gap layer, the propagation of the magnetic flux between the first magnetic portion and the other magnetic layer is suppressed.
In the method of manufacturing the thin film magnetic head of the invention, it is also possible that the other magnetic layer is formed as a single layer, a recess is selectively formed in a part of the other magnetic layer formed, and the magnetic shield layer is buried in the recess. Alternatively, the other magnetic layer is formed so as to have a stacked structure made by a plurality of layers, at least an opening is selectively formed in a layer adjacent to the gap layer upon formation of the stacked structure, and the magnetic shield layer is buried in the opening.
In the thin film magnetic head or the method of manufacturing the head of the invention, the magnetic shield layer may be formed so as to have the shape in plane corresponding to that of the overlap region.
In the thin film magnetic head or the method of manufacturing the head of the invention, the magnetic shield layer may be formed in a part of the other magnetic layer.
In the thin film magnetic head or the method of manufacturing the head of the invention, the magnetic shield layer may be formed in a in a part of the first magnetic portion.
In the thin film magnetic head or the method of manufacturing the head of the invention, the first magnetic portion comprises: a track width defining portion which extends with constant width so as to be apart from the recording-medium-facing surface and defines a recording track width of the recording medium; two or more connection portions which are magnetically coupled to a part of the second magnetic portion and are disposed so as to be apart from each other in the track width direction; and an intermediate coupling portion which has an edge for defining an edge on the recording-medium-facing surface of the insulating layer and magnetically couples the track width defining portion and the two or more connection portions, and the two or more connection portions and the second magnetic portion may overlap with each other in the overlap region.
In the thin film magnetic head or the method manufacturing the head of the invention, the magnetic shield layer may be formed so that the position of its edge on the recording-medium-facing surface side either coincides with the position of the edge on the recording-medium-facing surface side in the intermediate coupling portion of the first magnetic portion or is deviated from the position so as to be apart from the recording-medium-facing surface.
In the thin film magnetic head of the invention, a step in the width direction may be formed in a position where the track width defining portion and the intermediate coupling portion in the first magnetic portion are coupled to each other, in such a manner that the width of the track width defining portion is narrower than the width of the intermediate coupling portion at the coupling position. In this case, a step face of the intermediate coupling portion in the step may be substantially perpendicular to the extending direction of the track width defining portion.
In the thin film magnetic head according to the invention, it is preferable to form the first magnetic portion so that the width of the intermediate coupling portion is narrower than that of the connection region defined by the two or more connection portions, at the position where the intermediate coupling portion and the two or more connection portions are coupled to each other.
In the thin film magnetic head or the method of manufacturing the head of the invention, one of the magnetic layers may be further provided with a third magnetic portion which is formed between the first and second magnetic portions and magnetically couples the first and second magnetic portions together. In this case, it is preferable to dispose the third magnetic portion so as to overlap with both a part of the first magnetic portion and a part of the second magnetic portion.
According to the invention, a method of manufacturing a thin film magnetic head including: first and second magnetic layers magnetically coupled to each other and having respectively two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the method may comprise the steps of forming the first magnetic layer as a single layer; forming a recess in the thickness direction in a part of the first magnetic layer; forming a magnetic shield layer by burying a non-magnetic material in the recess of the first magnetic layer; forming the gap layer so as to cover at least the surface of each of the first magnetic layer and the magnetic shield layer; selectively forming the first magnetic portion serving as a part of the second magnetic layer in a predetermined region on the gap layer; forming the thin film coil in a region where the first magnetic portion is not formed in an upper region of the gap layer; forming the insulating layer so as to cover the thin film coil; and selectively forming a second magnetic portion as another part of the second magnetic layer on the insulating layer and the first magnetic portion so as to partially overlap with and so as to be magnetically coupled with the first magnetic portion in a region corresponding to the region in which the magnetic shield layer is formed.
According to the invention, a method of manufacturing a thin film magnetic head including: first and second magnetic layers magnetically coupled to each other and having respectively two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the method may comprise the steps of: forming the first magnetic layer as a stack structure having an opening in a predetermined region in at least the uppermost layer; forming a magnetic shield layer by filling the opening in the uppermost layer in the first magnetic layer with a non-magnetic material; forming the gap layer so as to cover the surfaces of the first magnetic layer and the magnetic shield layer; selectively forming the first magnetic portion serving as a part of the second magnetic layer in a predetermined region on the gap layer; forming the thin film coil in a region where the first magnetic portion is not formed; forming the insulating layer so as to cover the thin film coil; and selectively forming a second magnetic portion as another part of the second magnetic layer on the insulating layer and the first magnetic portion so as to partially overlap with and so as to be magnetically coupled with the first magnetic portion in a region corresponding to the region in which the magnetic shield layer is formed.
According to the invention, a method of manufacturing a thin film magnetic head including: first and second magnetic layers magnetically coupled to each other and having respectively two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the method may comprise the steps of. forming the first magnetic layer; forming the gap layer so as to cover the surfaces of the first magnetic layer; selectively forming a magnetic shield layer made of a non-magnetic material on the gap layer; selectively forming a first magnetic portion serving as a part of the second magnetic layer on the gap layer so that its part covers the magnetic shield layer; forming the thin film coil in a region where the first magnetic portion is not formed; forming the insulating layer so as to cover the thin film coil; and selectively forming a second magnetic portion as another part of the second magnetic layer on the insulating layer and the first magnetic portion so as to partially overlap with and so as to be magnetically coupled with the first magnetic portion in a region corresponding to the region in which the magnetic shield layer is formed.
Other and further objects, features and advantages of the invention will appear more fully from the following description.